A failed start printed "built without recomp-net, or bind/peer invalid" for every cause. A player whose system held the UDP port read first that the build had no netplay.
The library answers a refused bind, a listen address it cannot read and a peer address it cannot use with the same -1. main.cpp now does those steps again (it reads the listen address as the library does, looks up a name, binds without address reuse) and reports the system's answer. The sentence names a cause only when the system does: address in use, access denied (a port range Windows keeps for Hyper-V or WSL, a port below 1024 elsewhere), address not available. Any other error gets the number and the system's text. The peer address is named only when the listen address opened and the peer address cannot be read. The build is named only when it has no netplay.
The sentences are in netplay_exit_reason.c with unit cases; a source guard checks the wiring in main.cpp.
A netplay match that ends early returns both players to the lobby. The
runtime knew why (netplay_soft_exit's origin) but only printed it to
stdout, so players saw the lobby again with no reason. A boot-digest
mismatch (peers booted different BIOS images or boot settings) first
held a black window for the full 20 s admit-stall watchdog.
netplay_soft_exit now records a sentence for its origin, and the soft
return to the lobby puts it on the launcher's status line through
last_error (the room and browser views already show it). The dig0 gate
timestamps a mismatch; once the same pair of digests has held for 3 s,
the watchdog ends the match with its own reason. A peer that gets the
other side's BYE while it sees the same mismatch reports the mismatch,
not "the other player left". A CLI match prints the sentence to stderr.
The origin-to-text map and the grace decision live in
netplay_exit_reason.c, covered by netplay_exit_reason_test. Builds on
the previous commit's psx_lobby_set_last_error.
Alexandros Mandravillis